The present invention relates to a glass pane with a functional film and a conductive wire for providing a function of antifogging and/or antenna, and a process for producing the glass pane. In fact, the conductive wire is formed on a part of the functional film.
In recent years, there have been proposed automotive glass panes with various functional films such as color films for providing heat shielding, ultraviolet shielding, privacy and the like.
Japanese Patent Unexamined Publication JP-A-7-330379 discloses a color, transparent body having a transparent substrate, a color film formed thereon and a transparent protective film.
This color film contains (1) an oxide of at least one metal selected from the group consisting of Ti, Si, Zr, Ta, Sn and Zn, as a main component thereof, and (2) fine particles of metal and/or metal oxide, which are dispersed therein. JP-A-9-30836 discloses a glass pane with a light shielding film, and this film is prepared by applying a coating liquid containing an inorganic pigment (CuO, Fe2O3 and Mn2O3) and a silica sol (i.e., silica-precursor-containing sol). JP-A-9-156962 discloses a composition for forming a metal oxide film. This composition contains a metal salt and an alkanolamine. JP-A-6-40252 discloses an automotive glass pane having a portion through which the light emitted from a high-mounted stop lamp is transmitted. This portion is designed to have a higher visible light transmittance. U.S. Pat. No. 6,075,490, corresponding to JP-A-10-212137, discloses an automotive glass pane having a heat-shielding film formed on its inner side. This film is partially removed or modified to increase the visible light transmission therethrough. A conductive wire is formed on the heat-shielding film for providing a function of antenna and/or anti-fogging.
It is an object of the present invention to provide a glass pane with a functional film and a conductive wire, which is capable of providing an undistorted image or view taken through the glass pane.
According to the present invention, there is provided a glass pane comprising (a) a glass substrate having first and second major surfaces opposed to each other; (b) a functional film formed on the first major surface of the glass substrate by a wet method, the functional film comprising at least one oxide; and (c) a conductive wire prepared by printing a metal-containing paste on the functional film. The second major surface of the glass substrate has a depression at a position corresponding to the conductive wire, and this depression has a depth not greater than 1 xcexcm. It is needless to say that the second major surface of the glass substrate may have only a slight depression, that is, the depth being a positive depth slightly greater than 0 xcexcm.
According to the present invention, there is provided a process for producing the glass pane. This process comprises (a) applying a coating liquid to the first major surface of the glass substrate, thereby forming thereon a first precursory film; (b) subjecting the coated glass substrate to a first baking (preliminary baking) at a first temperature of 550-620xc2x0 C., thereby turning the first precursory film into a second precursory film; (c) printing a metal-containing paste on a part of the second precursory film, thereby forming thereon a precursory conductive wire; and (d) subjecting the coated glass substrate to a second baking (main baking) at a second temperature of 600-670xc2x0 C. which is higher than the first temperature, thereby turning the second precursory film and the precursory conductive wire into the functional film and the conductive wire, respectively. With this process, it is possible to adjust the above-mentioned depression to having a depth not greater than 1 xcexcm. Therefore, the image or view taken through the glass pane becomes undistorted. For example, even when the glass pane is used as an automotive rear window glass inclined at an angle of 45 degrees or less to horizontal, the rear image or view taken by the driver from the rear-view mirror through the rear window glass becomes undistorted. This can bring the driver safety and comfort.